Polygonal barrel accuracy and cleaning? HK & Glock

[springwalk]

Have folks found polygonal barrels like what Glock & HK use any more accurate or easier to clean as they say? Are lead heads to stay away from in these barrels? Do polygonal barrels have a longer life span?

 

[Erik M]

They are easier to clean because there are no sharp angles in the barrel as you would find in a standard rifled barrel.

 

[9mmepiphany]

Just for accuracy, the rifling used in H&Ks and Glocks are not the same.

H&K has been using polygonal rifling, a regular (all sides and angles equal) polygon shape which is twisted down the length of the barrel to impart spin to the bullet, since at least the G3 (rifle) and the P9S (pistol)

Glock does not.

 

[AK103K]

For some reason, my Glocks seem to take longer to clean than any of my traditional "rifled" barrels. I would have thought the opposite, but it doesnt seem to be the case.

I had a P7M13 a number of years back, but I dont remember it being as hard to get the barrel clean.

 

[9mmepiphany]

See my post above yours, re: rifling types

The Glock's irregular/imperfect rifling causes that

 

[Onmilo]

"IMPERFECT"!!
BLASPHEMY!!
Glock is PERFECTION squared to the power of Glock!!

My H&K USP Elite is miles ahead of My Glock pistols in accuracy potential.
Matter of fact, it is the MOST accurate .45 acp pistol I have ever owned, period and seriously.

My Glocks are wonderful guns, but the accuracy is meh compared to other 9mm handguns I own, owned, and have fired.

Not only is the manner of rifling different on the H&K verses the Glock the construction and metallurgical composition of the barrels are completely different.

No matter what any internet expert suggests to you, NEVER shoot plain, unjacketed, lead bullets in a pistol using polygonal rifling and I don't care if you clean your pistol religeously after every shooting session or not.
You likely do not know the Brinnell hardness factor of every lead bullet offered in 9mm on the market and some will lead a barrel much faster than others even at low or medium velocities.
The lead build up in the bore increases the pressures of each successive shot being fired until eventually the pressure is so high the barrel can no longer contain it and the gun KABOOMS.

As to being easier to clean,,,well,,,in my experience I use fewer patches to complete the job.
Are they easier to clean?
No. Cleaning is still the suckiest part of shooting!

 

[PO2Hammer]

I don't find Glock or HK barrels easier to clean than others.
My Sig barrels seem the easiest to clean FWIW.

 

[AK103K]

I agree, my SIG barrels have always been easier and faster to get clean, but it still amazes me that thats the case. I would have bet it would be the other way around.

All my HK's were extremely dirty guns to clean, but thats due to the fluted chambers. As far as I know though, my P7 was the only one with the polygonal rifling. My 91's, MP5, as well as a couple of G3's I shot and cleaned, all had traditional rifling. Were the later guns or versions of these models different?

 

[RUT]

>>For some reason, my Glocks seem to take longer to clean than any of my traditional "rifled" barrels<<

Interesting, as I find it to be quite the opposite.

 

[AK103K]

Are you using a brush and tight fitting jag with your patches?

 

[RUT]

I am using a brush in conjunction with an oversized patch. (no jag) Takes hardly any effort at all, and comes out as clean as the proverbial whistle.

 

[The Wiry Irishman]

I've always been under the impression that polygonal rifling offered less accuracy potential than traditional button rifling. I've never seen or heard of any top-end competitors in accuracy-centric competitions like bullseye or benchrest using anything other than button rifling. I also recall a technical document put out by Walther that claimed group sizes increased by 20% with polygonal rifling in their tests. I can't find that document right now, so take that with a grain of salt. I always thought that polygonal rifling was a cost-saving measure, as you can just forge the barrel around a mandrel and do some finish machining to smooth it up rather than spending time drilling/reaming/broaching a blank and cutting complex and precise grooves.

But then again, as has been pointed out, there are polygonal rifled guns that do have very good accuracy. HK as mentioned, as well as Desert Eagles. Noveske AR barrels are polygonal as well, and highly sought after, and although I have no personal experience with them, I hear they are also exceptionally accurate.

 

[Mac's Precision]

Glock barrels clean just fine. Use a bronze brush with a solvent of your choosing followed by a patch on a jag. Works fine. They clean better and better if you apply Eezox to the bore.

As for accuracy....conventional rifling or polygon rifling...both shoot better than 99% of most shooters.

Cheers
Mac.

 

[RUT]

>>conventional rifling or polygon rifling...both shoot better than 99% of most shooters<<

And there you have it folks!

 

[springwalk]

Rut, that gets old. Not everyone is disinterested or poor to mediocre shooters. I think we all strive to be better shooter and wanna know what products perform the best. If we all just settled and never asked questions about how things are made and why makers do it a certain way then it would be a pretty generic world.

 

[REAPER4206969]

I've never had any problem cleaning a Glock bore.

You people are doing it wrong.

 

[REAPER4206969]

I've always been under the impression that polygonal rifling offered less accuracy potential than traditional button rifling.

Polygonal rifling offers increased accuracy due to significantly less bullet deformation (rifling engraving.)

I always thought that polygonal rifling was a cost-saving measure, as you can just forge the barrel around a mandrel and do some finish machining to smooth it up rather than spending time drilling/reaming/broaching a blank and cutting complex and precise grooves.

Polygonal rifling is far more costly than Ballard rifling. HK/Glock/Walther/Kahr doesn't sound like the "cost-saving" types.

 

[The Wiry Irishman]

Polygonal rifling offers increased accuracy due to significantly less bullet deformation (rifling engraving.)

This definately seems logical. If this is the case, however, I'd be curious to see why it hasn't made inroads into things like benchrest or bullseye.

Polygonal rifling is far more costly than Ballard rifling. HK/Glock/Walther/Kahr doesn't sound like the "cost-saving" types.

What makes it more costly? As far as I'm aware there's less machining operations involved, and I don't think it would require any more precision than a high-end button rifled barrel. I'm no expert, and I could be wrong on either of those points, but I can't see what would make them cost more. Especially considering the polygonal rifling machines that GFM in Austria make can produce one barrel every three minutes or so. I'm not sure that's possible with traditional rifling. Granted, these machines are a massive initial investment that may up the price of the product, but I would think the speed and quantity would more than make up for it.

As far as HK, Walther, and Glock are concerned, their poly rifled guns are duty guns and to a degree they are building them to a price point, since their intended to be mass market guns adopted in large scale by various militaries and agencies, so I'm not sure arguing poly rifling isn't a cost-saving measure because they use it is valid. Kahr, on the other hand may be. Even if we assume cost and accuracy are equal for guns of this type, poly rifling would still be the way to go because of its longer barrel life.

Walther in particular of the manufacturer's you've mentioned is an interesting one. Their duty-type pistols use poly rifling, but they make competition guns as well, which are button rifled. You'd think they'd put the most accurate possible barrels in them, especially since price isn't really a consideration. Though it also could be because of poly rifling's issues with bare lead.

Anyway, you've probably noticed I've been using "I think" and "as far as I know" a lot, because, like I said, I'm no expert, I'm just drawing on manufacturing knowledge not specific to firearms. I'd like to hear your explanation of the higher cost of poly rifling.

 

[REAPER4206969]

If this is the case, however, I'd be curious to see why it hasn't made inroads into things like benchrest or bullseye.

I have little knowledge of the accuracy based gun games, however one of the most expensive and sought after Sniper/counter Sniper/DM rifles uses Polygonal rifling.

Heckler und Koch PSG-1

What makes it more costly?

Here's what Wiki has to say:

Part of the difference may be that most polygonal rifling is produced by hammer forging the barrel around a mandrel containing a reverse impression of the rifling. Hammer forging machines are tremendously expensive, far out of the reach of custom gunsmiths (unless they buy pre-rifled blanks), and so are generally only used for production barrels by large companies.
http://en.wikipedia.org/wiki/Polygonal_rifling

I don't think it would require any more precision than a high-end button rifled barrel.

We are not discussing high end barrels here. There would be little accuracy difference between a well made button rifled barrel Vs. a well made poly barrel. However, compare a production poly barrel to a production Ballard barrel and you may find an increase in accuracy. Let it be known that I'm not claiming poly barrels have a huge (or even noticeable) accuracy advantage. Accuracy is low on the poly advantage list IMO.

 

[GLOOB]

Polygonal barrels might have greater accuracy potential. But they DO give greater velocity out of a pistol length barrel. Stock 4.91" G20 barrels produce the same velocity as aftermarket 6" barrels.

 

[The Wiry Irishman]

Being a bit of a manufacturing nerd, this discussion piqued my interest and I've been doing some reading.

The obvious benefits of poly rifling that everyone knows are longer barrel life and a marginal, almost negligible increase in velocity. Downside, is, of course, heavy leading with unjacketed bullets.

Poly rifled barrels are indeed far cheaper to produce given you produce enough units. As Reaper pointed out, the machines to do it are massively expensive, so it only makes sense to go that route if you're a company like Glock that's churning out hundreds of thousands of units a year. That way the cost of the machine gets distributed across all these units for the life of the machine, which is quite long. Also the poly rifling machines have lower recurring costs as they require far more infrequent tooling changes.

Now as far as accuracy is concerned, in theory it appears that would have identical accuracy potential given equal manufacturing quality. Poly rifling does indeed deform the bullet less, but apparently the deformation imparted by high-end button rifled barrels is so uniform that it does not effect flight stability. The problem with poly rifling in reality, however, is because of the nature of the process that makes them so cheap to mass-produce makes it hard to control the regularity of the shape of each internal face and the elevation consistency of those faces. This can be controlled, however, to produce more accurate poly barrels like you see in pistols, but to achieve the highest levels of accuracy, you would be making them in a very similar to the way you make button rifled barrels, with a long series of time-consuming machining operations, effectively negating the cost difference between the two. That's why you don't see poly rifled barrels in any of the accuracy games. It has nothing to do with accuracy potential, its the fact that making a poly rifled barrel to that precision level would cost about the same as a button rifled barrel, so there's just no incentive to do it. Actually, it would probably be more expensive, since the manufacturer would have to invest in new tooling and reprogram their machines to the new process. Given equal accuracy, there's no benefit to a poly barrel in a competition gun. Velocity isn't a concern, and barrel life really isn't, either. Bullseye competitors are shooting very soft lead slugs that pretty much make standard rifling last forever, and rifle shooters are replacing barrels due to throat erosion well before the rifling starts to wear.

Now keep in mind these accuracy differences I'm mentioning are quite small, probably eclipsed by other accuracy factors in an autopistol, such as lockup consistency, not to mention the skill of the shooter.

From what I can tell, if you're looking at poly vs. button rifling in a handgun, the only question you should be asking is "Do I shoot lead?"

 

[9mmepiphany]

Thank you TWI

This is inline with what I remember about poly rifling, but I read it so long ago, didn't have the cites, and I'm not sure I understood it when I read it that I was reluctant to start down that road.

Much of the accuracy claims for polygonal rifle do come from the PSG-1, which had superlative accuracy standards/specs...but they weren't accomplished through careful fitting as you would thing sniper rifles are. HK-91/G3s were test fired, the most accurate were pulled off the assembly line and set aside to become PSG-1s...their receivers were reinforced with bars welded into the channels for the collapsing stock and a target grade trigger group was fitted.

 

[GLOOB]

I'm no expert, Irishman, but I understand button rifling to be the worst, in terms of consistency, particularly with maintaining a consistent twist rate, since the button turns itself. Also, the button can press deeper on one side than the other. Then, because the barrel is stress-relieved and countoured AFTER the rifling is formed, the diameter of the bore may not be uniform and need to be lapped. It is popular among custom barrel makers because the equipment is cheap. When you talk about HK picking the best rifles and calling them the PSG-1, that's basically what you get from a custom button rifled barrel-maker, too. Makers of button rifled barrels often sell different grades, because not every barrel comes out the same. Cut rifling is probably better for your analogy.

 

[The Wiry Irishman]

You bring up some interesting points, GLOOB. I haven't read much about cut vs. button for traditional rifling, but while researching for my previous post, I did come across mention that button rifling is exclusively used in competition air guns because the process leads to smoother and more laterally consistent grooves relative to cut rifling, but that was only one mention and did not go into detail of the machining processes. I'll have to do some reading on this, as well.

ETA - And I also was improperly using the phrase "button rifling" as a general catch-all for land-and-groove rifling as a whole.

 

[GLOOB]

Air gun barrels are also easier to produce with consistency, using the button rifling method. The steel isn't hardened much if any, and air guns barrels don't operate at high temp. So residual stress is not much of an issue.

Cut rifling is usually considered the better (as in more consistent and more expensive) of the two for firearms. It is also the only practical way to do custom twist rates.